A highly efficient sample introduction system for interfacing microfluidic chips with ICP-MS

Abstract

A sample introduction system specifically designed for interfacing laboratory on a chip devices with ICP-MS is presented. The development and optimisation of this highly efficient interface is described. This system uses an extremely low flow micro-cross-flow nebuliser (MCFN) sited directly at the liquid exit of the chip. An evaporation chamber has been incorporated into the interface in order to prevent the losses associated with traditional spray chambers, allowing the entire sample aerosol to enter the plasma. The optimised system achieved a sensitivity of 13500 cps for 10 μg L⁻¹ indium at 5 μl min⁻¹. The stability of the sample introduction over 10 min was 2.6% RSD (n = 453) and no sample recondensation was ever observed in the evaporation chamber at flow rates up to 20 μl min⁻¹. Hydrodynamic sample injection was performed via a manual switching valve, with a reproducibility of 5.10% RSD (n = 6). Sample volumes of >40 nl can be analysed. The advantages and potential applications, in particular for elemental speciation, are discussed.